Telemetering system



6, 1957 LAN J. WONG 2,802,205

TELEMETERING SYSTEM Filed July 19, 1954 3 Sheets-Sheet l ELECTRICALPOWER SUPPLY FIG.!

TE LEME TER TRANSMITTER INSULATION INSULATION IIVSU TION IN V EN TOR.

BYLAN J. Wo/ve M, (WM)- m ATTORNEYS Aug. 6, 1957 LAN J. WONG 2,802,205

TELEMETEIRING SYSTEM Filed July 19, 1954 s Sheets-Sheet 2 FIG. 4

INULAT/ON 35 p36 F/G. 2 16 *35 O 4 50 o /0 23 3 -1 8 IMSULAT/ON 8 22 ,33

20 I6 .r/NSl/LATION I an O I I O ,3,

' INSULATION 38 FIG. 3 v2 @52 mum/om 28 a 5.5 8

k INSULATION 5 H27 5/ 7 m Lies INVENTOR. LAN J. Wane M 4m, 11 64 n HISATTORNE Y5 -6,1957 LAN J. WONG 2,802,205

TELEMETERING SYSTEM Filed July 19, 1954 3 Sheets-Sheet 3 IN V EN TOR.

LA/v J WONG United States Patent TELEMETERING SYSTEM Lan J. Wong,CincinnatL'Ohio Application July 19, 1954, Serial No. 444,235

14 Claims. (Cl. 340359) This invention relates to digital telemeteringsystems for transmitting in the form of coded electrical pulses thenumerical values of one or more conditions which may vary with time.Objects and advantages of the invention will appear as the descriptionproceeds.

In a preferred embodiment of the invention, a telemeter transmitter hasa plurality of code drums, positioned side by side, rotatable about acommon axis. Each drum has an electrically non-conductive peripheralsurface with a plurality of conductive contact strips, of wide andnarrow width respectively, axially spaced apart thereon and eachextending circumferentially partway around the drum. An oscillatorycontact arm moves axially across the peripheral surfaces of the drumssuccessively, and as the contact arm crosses each contact strip anelectrical pulse is produced. A wide contact strip produces a relativelylong pulse, and a narrow contact strip produces a shorter pulse. Eachdrum has cm wide contact strip and four narrower contact strips soarranged on the peripheral surface that each of ten substantially equalsectors of the drum is different from any other such sector of the samedrum with respect to the number of wide and narrow contact stripsthereon. Consequently, as the contact arm crosses each drum, any one often different combinations of long and short pulses may be produced,depending upon the angular position of the drum. These pulses mayrepresent numbers in accordance with the following code:

Long pulses Short pulses Numerical value In the alternative embodiment,all of the contact strips on each code drum are substantially the samewidth, and a series of Zero to nine pulses of substantially equal lengthrepresent the digits zero to nine, respectively.

Means are provided for rotating the drums in accordance with changes invalue of the varying condition. Each drum is connected to the nextadjacent drum through intermittent gearing such that as one drumcompletes a full revolution the next drum is rotated by onetenthrevolution. Thus three drums are sufiicient to produce coded electricalpulses respectively representing one thousand different numerical valuesof the varying condition. The telemeter receiver preferably includes anelectrical chart recorder for displaying a record of the pulses on astrip of chart paper; but it should be understood that other types ofreceiver may also .beused, such as a receiver having means for printingthe respective digits represented by each series of pulses.

Either before or after crossing the code drums, preferably before, theoscillating contact arm crosses a series of fixed contacts and therebyproduces a coded series of pulses which identifies the transmitter.Several transmitters may be used in the same telemetering system totransmit selectively the numerical values of several different varyingconditions. The several transmitters may be similar except that each hasits own distinctive arrangement of fixed contacts which produce, eachtime that transmitter is operated, a distinctively coded series ofpulses which identifies the transmitter in the permanent recorddisplayed on the receiver chart. If desired, the receiver may also beprovided with a conventional time-stamp mechanism for printing on thechart thetime when each recording is made, so that the receiver chartcontains a permanent record of the transmitter identification, the

numerical values transmitted, and the time.

The invention will be better understood from the following descriptiontaken in connection with the accompanying drawings, and its scope willbe pointed out in the appended claims. In the drawings,

Fig. .1 is a schematic plan view showing an illustrative embodiment ofmy telemetering system, with inner and outer cover plates removed fromthe transmitter drum box,

Fig. 2 is a plan view of the transmitter drum box with the inner coverplate in place,

.Fig. 3 is a plan view of the transmitter drum box with the outer coverplate in place,

Fig. 4 is a section view taken generally along the line 44 of Fig. 1,with both inner and outer cover plates in place,

Fig. 5 is a developed view of the peripheral surface of a code drum,showing a preferred arrangement of the contact strips, and

Fig. 6 is a developed view of the peripheral surface of a code drum,showing an alternative arrangement of the contact strips.

Fig. 7 is a cross-sectional view of cover-plate 51 taken on the line 7-7of Fig. 3.

Referring now to Figs. 1 through 5, inclusive, the drawings illustrate atelemetering system used to indicate liquid levelfor example, the waterlevel in a river. A fioat 1, which rides on the surface of the water, isconnected to one end of a cable 2 which encircles a drum 3. The cable iskept taut by suitable means such as a weight 4 attached to its otherend. Drum 3 is connected through shaft '5, gear 6 and gear 7 to theinput shaft 8 of the telemeter transmitter. Float 1 rises and falls withchanges in the water level, and through the linkage shown rotates shaft8. Thus shaft 8 is rotated in accordance with changes in the water levelof the river. It will be appreciated that other means may be employed torotate shaft 8 in accordance with changes in the value of any varyingcondition which it is desired to transmit, such as the amount ofrainfall collected in a suitable vessel, the weight of material placedon a scale, or any other measurable value.

The transmitter is mounted on a base plate 9, which in practice may beattached to, or a part of, a case (not shown) enclosing and protectingthe transmitter. The inputshaft 8 extends through the transmitter drumbox .10, as shown, and is connected through gears 11 and 12 pulses whichcorrespond to the three digits displayed by counter 13.

Shaft 8 is connected through gears 14 and 15 to a first code drum 16.Drum 16 is connected through intermittent gearing 17 to a second codedrum 18. The gearing 17 may be a set of Geneva gears or the like, suchas are commonly used in mechanical counting devices, to rotate drum 18one-tenth revolution as drum 16 completes each full revolution. Drum 18is similarly connected through intermittent gearing 19 to a third codedrum 20, so that drum 20 is rotated one-tenth revolution as drum 18completes each full revolution. Thus drums, 16, 18 and 20 are rotated toangular positions which correspond respectively to the right, center andleft digits 'displayed'by counter 13.

Fig. is a developed view showing the peripheral surface of drum 16.Thesurfaces of drums 16, 18 and 20 preferably are identical.Axiallyspaced apart on the peripheral surface of the drum are arelatively wide contact strip 21 and four narrow contact strips 22, 23,24 and 25. Preferably, the wide contact strip is about three times aswide as a narrow contact strip. Each of the narrow strips is dividedinto two circumferentially spaced-apart sections, the second section ofstrips 22, 23, 24 and 25 being shown at 22', 23', 24, and'25'respectively. t

In a preferred construction of the code drums, the contact strips arethe exposed rims of metal washers em-v bedded in a phenolic plasticwhich forms the body of the drum and provides an electricallynon-conductive peripheral surface except where the metal washers areexposed. A part of the rim of each washer is cutaway and the space thusleft is filled with non-conductive plastic to form the contact striparrangement shown in the drawings. All of the contact strips areelectrically conductive, and are electrically grounded to base plate 9through drum 'box and a metal shaft 26 upon which drums 16, 18 and arerotatably mounted. The contact strips may be chrome flashed to resistcorrosion and wear.

Referring especially to Fig. 5, it will be noted that each of tensubstantially equal sectors of drum 16 differsfrom every other suchsector with respect to the number of wide and narrow contact strips onits surface. Starting at the bottom of Fig. 5, the first sector 27,representing the digit 0, contains no contact strip; the second sector28, representing the digit 1, contains one narrow contact strip; thethird sector 29, representing the digit 2, contains two narrow contactstrips; the fourth sector 30, representing the digit 3, contains threenarrow contact -strips; the fifth sector 31, representing the digit 4,contains four narrow contact strips; the sixth sector 32, representingthe digit 5, contains one wide contact strip; the seventh sector 33,representing the digit 6, contains one wide and one narrow contactstrips; the eighth sector 34, representing the digit 7, contains onewide and two narrow contact strips; the ninth sector 35, representingthe digit 8, contains one wide and three narrow contact strips; andthetenth sector 36, representing the digit 9,

contains one wide and four narrow contact strips. Each sector containsthe same number of narrow contact strips as the diametrically oppositesector, but only the last five sectors contain the wide contact strip.Referring especially to Figs. 1 and 4, an oscillatory contact arm has anon-conductive part 37, preferably made of phenolic plastic, and aconductive part 38, preferably made of a metal such as Phosphor bronze,fastened together by suitable means such as rvets 39. Two electricalcontact points 40 and 41, preferably made of plati- -num alloy to resisttarnish and corrosion, are attached to the tip of part 38 on its top andbottom, respectively.

' One end of the contact arm is pivoted on a post 42 so that the otherend of the contact arm, which carries points 40 and 41, can move backand forth in the axial direction of code drums 16, 18 and 20.

In operation of the transmitter. the contact arm is I connected directlyto the signal channel. appreciated that the telemetering signal channelmay in- ;heads and plate 51, as shown.

oscillated by means hereinafter described in such a way that contact 41is raised away from engagement with the code drums as the contact armmoves from right to left, and is lowered to touch the peripheralsurfaces of the drums as the contact arm moves from left to right. Thus,during each oscillatory cycle of the contact arm, point 41 moves in asubstantially axial direction from left to right across the tops of codedrums 20, 18 and 16, successively. During such movement, point 41touches and crosses a number of the contact strips which depends uponthe respective angular positions of the code drums, and hence dependsupon the numerical value of the water level or other variable conditionto be transmitted.

Whenever point 41 of the contact arm touches the electrically groundedcontact strips, an electrical circuit is completed from electrical powersupply 43 through the winding of a relay 44, current-limiting resistor45, contact arm parts 38 and 41, and the contact strips. Current flowsin this circuit while point 41 crosses the contact strip, and forms anelectrical pulse of a length which depends upon the velocity of point 41and the width of the contact strip being crossed. The wide contactstrips produce relatively long pulses, and the narrow contact stripsproduce short pulses. Each such pulse operates relay 44 to close relaycontacts 46 and produce a similar but amplified pulse in thetelemetering signal channel represented by wires 47 and 48.

The chief purpose of relay 44 is to amplify the pulses. Where weaksignals are permissible in the telemetering channel, relay 44 may beomitted and the contact arm It will also be clude, in place of or inaddition to wires 47 and 43, a radio link or any other means fortransmitting electrical pulses.

To keep the tip of the contact arm from dropping into the spaces betweenthe code drums, the drum box is provided with an inner cover plate 49,as shown in Figs. 2 and 4.- This inner cover plate is made ofelectrically non-conductive material, such as phenolic resin or otherplastic, and is fastened in place by suitable means such as screws 50.Plate 49 covers the gears in the drum box and includes a plurality oftongues 49 which extend between and on each side of the code drums, asshown. The tops of tongues 49 are level with the tops of the code drums,so that a substantially smooth non-conductive surface is provided forcontact point 41 to ride upon as it moves from one code drum to another.

An outer cover plate 51, shown in Figs. 3 and 4, is fastened to the topof the drum box by screws 52. Plate 51, preferably made of phenolicplastic, has a flat nonconductive bottom surface which contact point 40slides across as the contact arm moves from right to left during itsoscillatory cycle. Eight holes, which extend through plate 51 along aline substantially parallel to the axis of the code drums, are threadedto receive metal screws 53 and plastic screws 54. The lower ends ofscrews 53 and 54, which are substantially flush with the bottom of plate51, are crossed by contact point 40 as it moves from right to leftacross the bottom of the outer cover plate.

The heads of screws 53 are in electrical contact with a metal plate 55,which is fastened between the screw Plate 55 is electrically grounded tobase plate 9 through lead 55, screw 52 and drum box 10.

The electrically grounded metal screws 53 serve as .contact 41 crosses acontact strip of the code drums.

pulse is produced in the same manner as occurs when When severaltransmitters are used in the same telemetering system, different numbersor arrangements of metal screws 53 are used in the differenttransmitters, so that .eachtransmitter produces its own, distinctivelycoded rail series of identification pulses which differs from thatof theother transmitters. Plastic screws '54, which are nonconductive, fillthe unused holes in plate 51 to maintain a substantially flat surfacefor contact point 40 to slide across. The identification code of anytransmitter can be changed quickly and easily, whenever desired, byremoving screws 53 and 54 and replacing themin difierent proportions orsequences in the eight holes provided.

The means for oscillating the contact arm includes an electric motor 56mounted beneath a motor bracket 57. Through conventional speed-reducinggearing inside the motor housing, motor 56 rotates a cam shaft '58andcam 59 in a clockwise direction. A pin 60, attached to cam 59parallel with and eccentric to shaft 58, engages a lengthwise slot 61 inthe contact arm and oscillates the contact arm about its pivot at 42through an arc of about twenty degrees. This oscillation moves thecontact arm tip carrying contact points 40 and 41 back and forthsubstantially parallel to the axis of the code drums in the spacebetween the tops of the code drums and the bottom of plate 51.

During the time that pin 60 is moving the contact arm from right toleft, cam 59 engages a hinged'fiap 62 which in turn engages the bottompart 37 of the contact arm and raises the arm so that contact 41 islifted away from engagement with the code drums and contact 40 isbrought into engagement with the bottom of plate .51 and crosses thefixed contact screws 53 to produce the coded series of transmitteridentification pulses. During the remainder of the oscillatory cycle,when the contact arm moves from left to right, cam 59 permits-flap 62and the contact arm to drop sufficiently so that contact point 40 dropsout of engagement with plate 51 and contact point 41 is brought intoengagement with and successively crosses the code drums 20, 18 and 16 toproduce the coded series of pulses which represent the numerical valueto be transmitted. A stop 63 limits the downward motion of the hingedflap 62 so that it remains in a favorable position to re-engage cam 59at the beginning of the next cycle.

Since the cam shaft and cam rotate in the clockwise direction as viewedin Fig. 1, pin 60 is nearer pivot 42 during right-to-left motion of thecontact arm than it is during left-to-right motion. Consequently, theright-toleft motion is somewhat faster, and is completed in slightlyless than one-half of the oscillatory cycle. This leaves more time forthe contact arm to move across the code drums, and thus provides betterresolutionof the pulses representing numerical values without increasingthe total cycle time. Because of the relatively rapid motion of thecontact arm across screws 53, the transmitter identification pulses arerelatively short despite the substantial width of the screws.

On the other hand, variations in velocity of the contact arm as itcrosses the code drums causes some variation in the length of pulsesproduced as different contact strips are crossed. However, using widecontact strips about three times the width of the narrower contactstrips, I have experienced no difliculty in distinguishing the longpulses from the short pulses. If required, the variations in pulselength due to contact arm velocity changes can be minimized oreliminated by compensating variations in the widths of the Contactstrips, making the strips narrower where the contact arm velocity islowest and wider where the velocity is greatest. For manufacturing andmaintenance convenience, however, I prefer to avoid such compensationsand to make all of the code drums identical.

Between oscillatory cycles, the contact arm stops at a rest position,illustrated in Fig. 1, at the right end of its oscillatory path. In thisrest position, the contact arm engages a switch lever 64 which opens anormally-closed switch 65.

To operate the transmitter and initiate an oscillatory .cycleofthecontact arm,.a.-normally-open starting switch '66 is held closedfor a few moments, to complete a .circuit-from'power supply 43 to astarting relay 67. This closes the relay contacts and supplies electricpower through leads 69 and 70 to start motor 56. As the motor starts itrotates cam 59 and moves the contact arm .to the left away from its restposition. Switch 65 now closes, and since it is connected in parallelwith relay contacts 68, it continues to supply electric power to operatemotor 56, even though switch 66 may now be released and reopen. Themotor continues to operate until an oscillatory cycle has been completedand the contact arm returns to the rest position. The contact armthenengages level 64 to open switch 65, and the motor stops until switch 66is closed again.

As the contact arm successively crosses the fixed contacts 53 and thecode drums 20, 18 and 16, electrical pulses are produced as hereinbeforeexplained and the pulses are transmitted over the telemetering signalchannel comprising wires 47 and 48. These pulses are received by:receiver apparatus including an electrical chart recorder 71 WhIChdisplays the pulses on a strip of chart paper 72. The'firstcoded seriesof pulses received, displayed at 73,

identifies the transmitter. The next three series of pulses, displayedat 74, 75 and 76, respectively, represent the numerical valuetransmitted, which in the case illustrated is the number'791.

Another transmitter 77, responsive to numerical values ofanother'varying condition and having its identification code screwsdiiferently arranged, but otherwise identical to the transmitterhereinbefore described, may be connected to the same telemetering signalchannel. Transmitter 77 is operated by closing its starting switch 78,whereupon it transmits pulses which are displayed by receiver 71. Theseries of identification pulses, which is different for eachtransmitter, permanently identifies on the receiver chart thetransmitter, and hence the varying condition, to which the numericalvalues which follow are related. Because of this feature, manytransmitters may be connected to the same telemetering channel withoutrisk of confusing the recorded data.

Fig. 6 is a developed view showing the peripheral surface of analternative code drum 16 which may be used in place of the code drum 16.Alternative drums 18 and 20, similar to drum 16 and therefore notillustrated, may be used in place of drums 18 and 20, respectively.Axially spaced apart on the peripheral surface of drum 16' are ninecontact strips, 79 through 87, inclusive, all substantially equal inwidth but different in length. These contact strips are so arranged onthe drum surface that each of ten substantially equal sectors of drum 16differs from every other such sector with respect to the number ofcontact strips on its peripheral surface. The ten drum sectors contain0, l, 2, 3, 4, 5, 6, 7, 8 and 9 contact strips, respectively, whichproduce a corresponding number of electrical pulses of substantiallyuniform length when the oscillatory contact arm moves across a sector ofdrum 16'. With this arrangement, the number of pulses in each series isthe same as the digit represented thereby. Except for the differentcontact strip arrangement, drum 16 is preferably identical to drum 16,although it may be made somewhat wider to accommodate the larger numberof contact strips more easily.

My invention is not limited to the specific embodiments hereinillustrated and described. It is intended that the following claimsshould cover all changes and modifications which do not depart from thetrue spirit and scope of the invention.

I claim:

1. A telemeter transmitter comprising at least one rotatable drum havingan electrically non-conductive peripheral surface, a plurality ofconductive contact strips axially spaced apart on said peripheralsurface and each extending circumferentially part-way around said drum,a fixed plate having a non-conductive surface facing said ,contact armback and forth on said surface of said plate along a line substantiallyparallel to the axis of said drum, an oscillatory contact I arm movablesubstantially parallel to said drum axis between sa1d plate and saiddrum, means to move said arm parallel to said drum axis back and forthin oscillatory cycles, means moving said arm into contact with saidplate as said arm moves in one direction of its oscillatory motion andinto contact with said drum as said arm moves in the opposite direction,and means producing an electrical pulse each time said contact armtouches any of said fixed contacts and said contacts strips.

2. A telemeter transmitter comprising at least one rotatable drum havingan electrically non-conductive peripheral surface, a plurality' ofconductive contact strips axially spaced apart on said peripheralsurface and each extending circumferentially part-way around said drum,a fixed plate having an electrically non-conductive bottom surfacepositioned above and spaced apart from said drum,

. said plate having a plurality of threaded holes therethrough along aline substantially parallel to the axis of said drum, a plurality ofremovable screws within said holes' extend ing downward to the bottomsurface of said other end of said arm' beingmovablesubstantiallyparallel to said drum axis between said plate and saiddrum, said armhaving a lengthwise slot, a cam and cam shaft, a

. motor operable to rotate said cam and cam shaft, a pin mounted on saidcam parallel with and eccentric to said cam shaft, said pin'engagingsaid slot to move said in oscillatory cycles as said cam shaft rotates,a hinged flap engaging said camjduring substantially one-half of eachrevolution of said cam shaft, said cam during such engagement movingsaid hinged flap upward into engagement with said arm and therebylifting said arm away from contact with said drum into contact with saidplate,

whereby said arm touches the peripheral surface of said .dmm as it movesacross the drum in one direction and touches said plate as it movesacross in the other direction, and means producing an electrical pulseeach time said contact arm touches any of said fixed contacts and saidcontact strips.

'3. A telemetering system for transmitting numerical values of a varyingcondition, comprising at least one rotatable drum having an electricallynon-conductive peripheral surface, a plurality of conductive contactstrips axially spaced apart on said peripheral surface and eachextending circumferentially part-way around said drum,

- said strips being of wide and narrow widths respectively and being soarranged that each of ten substantially equal .sectors of said drum isdifferent from any other such sector with respect to the number of wideand narrow contact strips thereon, means rotating said drum selec tivelyto a plurality of angular positions corresponding to respectivenumerical values of the varying condition, a

fixed plate having a non-conductive surface facing said drum, aplurality of fixed conductive contacts spaced apart on said surface ofsaid plate along a line substantially parallel to said drum axis, anoscillatory contact arm movable substantially parallel to said drum axisbetween said plate and said drum, means including an electric motoroperable to move said arm back and forth in oscillatory cycles, meansmoving said arm into contact with said plate as said arm moves in onedirection and into contact with said drum as said arm moves in the otherdirection,

. said arm having a rest position at one end of its oscillation path,electrical circuit means for starting said motor to initiate anoscillatory cycle of said arm, means including a normally-closedelectric switch for operating said motor to complete the oscillatorycycle of said arm, means engaging said arm and opening said switch whensaid arm returns to its rest position, means producing long'and shortelectrical pulses as said contact arm touches and crosses said wide'andnarrow contact strips respectively and producing other electrical pulsesas said contact arm touches and crosses said fixed contacts, and areceive which records said pulses.

4. A telemeter transmitter comprising a frame, at least one coding drummounted for rotation within said frame, means for rotating said drumselectively -to a plurality of angular positions in accordance with avarying condition, an arm pivotally supported at one end upon saidframe, electrical contact means on the other end of said arm, meansoperable to oscillate said arm about its pivotal support to traversesaid other end of said arm from a rest position back and forth acrossthe peripheral surface of said drum in a direction substantiallyparallel to the axis of rotation of said drum, electrical contact meansupon the peripheral surface of said drum for indicating the angularposition of said drum with respect to said frame, electrical contactmeans fixedly mounted upon said frame in alignment with the path ofmovement of said arm, and means cooperative with said oscillating meansfor engaging said contact means on said arm with said contact means onsaid drum during movement of said arm in one direction across said drumand for engaging said contact means on said arm with said contact meanson said frame during movement of said arm in the other direction acrosssaid drum.

5. A telemeter transmitter as recited in claim 5 wherein the means foroscillating the arm comprises a constant speed motor, a pineccentrically secured to the motor shaft and engaging a slot in saidcontact arm whereby said arm is moved across said contact means on saidframe at a velocity greater than the velocity at which said arm is movedacross the peripheral surface of said drum.

6. A telemeter transmitter as recited in claim 5 wherein said electricalcontact means on said drum comprises a plurality of axially spacedcontact strips embedded in said drum, each 'of said strips being ofdifferent circumferential extent to define a plurality of sectors on theperipheral surface of said drum, each of said sectors being differentfrom any other sector with respect to the number of contact stripsthereon.

7. A telemeter transmitter as recited in claim 7 wherein the means foroscillating the arm comprises a constant speed motor, a pineccentrically secured to the motor shaft and engaging a slot in saidcontact arm whereby said arm is moved across said contact means on saidframe at a velocity greater than the velocity at which said arm is movedacross the peripheral surface of said drum.

8. A telemeter transmitter as recited in claim 8 wherein each of saidcontact strips comprises an exposed portion of the rim of a metalwasher, the exposed portion of said washer having a diameter equal tothe diameter of said drum.

9. A telemeter transmitter comprising a frame, a plurality of codingdrums mounted for rotation about a common axis within said frame, meansfor rotating said drums selectively to a plurality of angular positionsin accordance with a varying condition, an arm pivotally supported atone end upon said frame, electrical contact means on the other end ofsaid arm, means operable to oscillate said arm about its pivotal supportto traverse said other end of said arm from a rest position back andforth across the peripheral surfaces of said drums in a directionsubstanmovement of said arm in the other direction.

10. A telemeter transmitter as recited in claim 9 wherein the means foroscillating the arm comprises a constant speed motor, a pineccentrically secured to the motor shaft and engaging a slot in saidcontact arm whereby said arm is moved across said contact means on saidframe at a velocity greater than the velocity at which said arm is movedacross the peripheral surfaces of said drums.

11. A telemeter transmitter as recited in claim 9 wherein said drums areaxially spaced from each other and means are provided in the spacebetween respective drums to maintain said arm in alignment with theperipheral surfaces of adjacent drums during movement of said arm fromthe peripheral surface of one drum to the peripheral surface of anadjacent drum.

12. A telemeter transmitter as recited in claim 11 wherein the means foroscillating the arm comprises a constant speed motor, a pineccentrically secured to the motor shaft and engaging a slot in saidcontact arm whereby said arm is moved across said contact means on saidframe at a velocity greater than the velocity at which said arm is movedacross the peripheral surfaces of said drums.

13. A telemeter transmitter comprising a plurality of axially spacedelectrically conductive washers, each of said washers having a portionof its circumferential surface in the shape of a circular arc, saidWashers being embedded in a body of electrically non-conductive materialwith the aforementioned circumferential surface portions of said Washerscooperating with the peripheral surface of said body to define a smoothcylindrical surface, means for connecting said washers into a first partof an electrical circuit, and contact means connected to a second partof said electrical circuit and movable into engagement with theperipheral surface of said body and the circurn ferential surfaceportions of said washers to selectively connect and disconnect the firstand second parts of said electrical circuit.

14. A telemeter transmitter as recited in claim 13 wherein the length ofthe circumferential surface portion of each of said washers is dilferentthan the length of the circumferential surface portion of other washerswhereby the peripheral surface of said cylindrical body is divided intoa plurality of sectors, each of said sectors being different from anyother sector with respect to the number of surface portions of saidwashers therein.

References Cited in the file of this patent UNITED STATES PATENTS873,270 Schmidt Dec. 10, 1907 1,638,417 Sperry Aug. 9, 1927 1,641,198Roucka Sept. 6, 1927 1,955,043 Yates et a1. Apr. 17, 1934 2,239,094Harvey Apr. 22, 1941 2,466,099 Hansen Apr. 5, 1949 2,588,102 Forero Mar.4, 1952 OTHER REFERENCES Publication: Remote Water-Stage, Electronics,"

Feb. 1945, pages -132, 340-203.

